so first

he need to check if false king didnt realized of that place, normally the eyes of false would be seen in heaven in that case or snowstorms in case of icy

doomy first will be ''peacefully'' and barely kills someone

but once the offer of a purgatory is regretted or answered by violence, he immediatly send the strongest that he has, or practically himself to unleash hell without mind if it can cause the destruction

probably both universes would have to pass atleast chaos

incase of icy or any god would immediatly choose violence

false king would visit the dynos or any other universe only and exclusively for his fun